Watercress, Nasturtium officinale, seems to be proliferating a bit more in the drainage pond than it did last year. It is difficult to compare, since I was not concerned about it enough to monitor it last year. I am likely noticing it more now because the duckweed, Lemna minor, deteriorated slower than it did last year, which maintained my interest in such infesting aquatic vegetation. I have been monitoring the cattail, Typha latifolia, also. Although none of these species are exotic, I do not want any of them to proliferate so much that they obscure the pond that they inhabit. That has been a problem with duckweed as long as the pond has contained water. I am aware that cattail also has potential to proliferate aggressively, although I believe that such proliferation would be easier to mitigate. I really do not know how watercress behaves, though. I can not remember ever seeing a pond anywhere completely overwhelmed by it. I doubt that, even if it does proliferate aggressively, that it would be as difficult to contend with as duckweed is. Perhaps it would compete with duckweed! Goodness; I never intended to get so involved with aquatic vegetation. It is not exactly the sort of vegetation that inhabits ‘land’scapes. Yet, the drainage pond is a feature of the landscapes here. We maintain the willows, cottonwoods, sycamores, oaks and Landon’s tree around it, so obviously, must maintain the aquatic vegetation within it as well. In that regard, I would prefer to grow a few more ornamental but less aggressive aquatic species, such as water lilies. Unfortunately, the few water lilies that we tried were tropical species that seemed to succumb to cool winter weather and overwhelming duckweed. I should try some native water lilies, but they might be a bit too prolific.
Tony Tomeo 